The present invention relates to a variable displacement swash plate compressor.
Japanese Laid-Open Patent Publication No. 5-172052 and Japanese Laid-Open Patent Publication No. 52-131204 each disclose a variable displacement swash plate compressor (hereinafter referred to as compressor). Each compressor is provided with a housing including a suction chamber, a discharge chamber, a swash plate chamber, and a plurality of cylinder bores. The housing rotatably supports a drive shaft. The swash plate chamber accommodates a swash plate, which is rotated when the drive shaft rotates. A link mechanism is arranged between the drive shaft and the swash plate to change an inclination angle of the swash plate. The inclination angle is an angle relative to a direction orthogonal to the rotation axis of the drive shaft. A piston accommodated in each cylinder bore reciprocates and forms a compression chamber in the cylinder bore. When the swash plate rotates, a conversion mechanism reciprocates the piston in each cylinder bore with a stroke corresponding to the inclination angle. A control mechanism controls an actuator to change the inclination angle.
In the compressor of Japanese Laid-Open Patent Publication No. 5-172052, a pressure adjustment chamber is formed in a rear housing segment of the housing. Further, a control pressure chamber that is in communication with the pressure adjustment chamber is formed in a cylinder block of the housing. The actuator is arranged in the control pressure chamber so as not to rotate integrally with the drive shaft. Specifically, the actuator includes a non-rotation movable body that covers a rear end of the drive shaft. An inner surface of the non-rotation movable body supports the rear end of the drive shaft so that the drive shaft is rotatable relative to the non-rotation movable body and movable in the axial direction. An outer surface of the non-rotation movable body is movable in the axial direction in the control pressure chamber but not about the rotation axis. A pushing spring is arranged in the control pressure chamber to urge the non-rotation movable body toward the front. The actuator includes a movable body that is coupled to the swash plate and movable in the axial direction. A thrust bearing is provided between the non-rotational movable body and the movable body. A pressure control valve is arranged between the pressure adjustment chamber and the discharge chamber to change the pressure in the control pressure chamber and move the non-rotation movable body and the movable body in the axial direction.
The link mechanism includes a movable body and a lug arm, which is fixed to the drive shaft. The rear end of the lug arm includes an elongated hole that extends toward the rotation axis from the outer side in a direction orthogonal to the rotation axis. A pin is inserted into the elongated hole to support the front side of the swash plate so that the front side is tiltable about a first tilt axis. The front end of the movable body includes an elongated hole that extends toward the rotation axis from the outer side in a direction orthogonal to the rotation axis. A pin is inserted to the elongated hole to support the rear side of the swash plate so that the rear side is tiltable about a second tilt axis, which is parallel to the first tilt axis.
In the compressor, the pressure adjustment valve is controlled to open and connect the discharge chamber and the pressure adjustment chamber so that the pressure of the control pressure chamber becomes higher than the pressure of the swash plate chamber. This moves the non-rotation movable body and the movable body forward. As a result, the inclination angle of the swash plate increases, and the stroke of the pistons increases. The compressor displacement of the compressor for each drive shaft rotation also increases. When the pressure adjustment valve is controlled to close and disconnect the discharge chamber and the pressure adjustment chamber, the pressure of the control pressure chamber decreases to the same level as the pressure in the swash plate chamber. This moves the non-rotation movable body and the movable body rearward. As a result, the inclination angle of the swash plate decreases, and the stroke of the pistons decreases. The compressor displacement of the compressor for each drive shaft rotation also decreases.
In the compressor disclosed in Japanese Laid-Open Patent Publication No. 52-131204, an actuator is arranged in the swash plate chamber and rotated integrally with the drive shaft. Specifically, the actuator includes a fixed body fixed to a drive shaft. A movable body that moves in the axial direction and is movable relative to the fixed body is accommodated in the fixed body. A control pressure chamber that moves the movable body with the interior pressure is defined between the fixed body and the movable body. A communication passage, which is connected to the control pressure chamber, extends through the drive shaft. The pressure control valve is arranged between the communication passage and the discharge chamber. The pressure control valve changes the pressure in the control pressure chamber to move the movable body in the axial direction relative to the fixed body. The rear end of the movable body is in contact with a hinge ball. The hinge ball is couple to the swash plate so that the hinge ball is tiltable. A pushing spring urges the rear end of the hinge ball in a direction that increases the inclination angle.
The link mechanism includes the hinge ball and the link, which is arranged between the fixed body and the swash plate. A pin, which extends in a direction orthogonal to the rotation axis, is fitted to the front end of the link. A pin, which extends in a direction orthogonal to the rotation axis, is fitted to the rear end of the link. The link and the two pins tiltably support the swash plate.
In the compressor, the pressure adjustment valve is controlled and open to connect the discharge chamber and the pressure adjustment chamber so that the interior of the control pressure chamber has a higher pressure than the swash plate chamber. This moves the movable body toward the rear, decreases the inclination angle of the swash plate, and decreases the stroke of the pistons. The compressor displacement per one rotation of the compressor also becomes small. On the other hand, if the pressure adjustment valve is close controlled to non-connect the discharge chamber and the pressure adjustment chamber, the interior of the control pressure chamber becomes a low pressure of the same extent as the swash plate chamber. The movable body thereby moves forward. The inclination angle of the swash plate thus becomes large, and the stroke of the piston increases. This increases the compressor displacement for each drive shaft rotation of the compressor.
In the compressors described above, a portion of the actuator easily inclines relative to the rotation axis when the suction reaction force and a compression reaction force of the pistons act on the actuator through the swash plate, the link mechanism, and the like. This adversely affects the operation of the actuator in such compressors and the control for varying the compressor displacement.